Process for detanning mineral or chrome tanned leather or leather-waste.



, tracting processalso lasted too long.

UNITED STATES PATENT OFFICE.

ALBERT RUDOLF WEISS, JR., OF H ILCHENBACH, GERMANY. PROCESS FOR DETANNING MINERAL 0R CHROME TANNED LEATHER 0R LEATHER-WASTE.

Specification of Letters Patent.

Patented 39v. 27, 19L 6.

Application filed October 21, 1903. Serial No. 177,976.

To all whom it may concern.-

Be it known that I, ALBERT RUnoLF WEISS, Jr. a subject of the German Emperor, residing at Hilchenbach, Westphalia, in the Kingdom of Prussia, Germany, have invented certain new and useful Improvements in an Improved Process for Detanning Mineral or Chrome Tanned Leather or Leather-Waste, of which the following is a s ecification.

The present invention relates to a new or improved method or process whereby mineral-dressed materials--such, for instance, as chrome-tanned leather or leatherwastecan have the tanning substance removed for the purpose-of making gelatin or glue therefrom.

As is known, several attempts have al ready been made to prepare leather-waste by suitable treatment in such a way that gelatin and glue can be produced therefrom. Thus a process is already known whereby barktanned or chamoised leather-waste is treated first with alkalies or quicklime and then with oxalic acid. Furthermore, attempts have been made to remove the tannin from leatherwaste with the aid of sulfuric acid, this process being especially applicable to leatherwaste. The first-named process did not prove suitable even for bark-tanned or chamoised leather. For mineral-tanned, and especially chrome-tanned, leather it has not been used at all, as such tanned leathers were quite unknown at the time, and a process 'which had failed with bark-tanned and chamoised leather would not have been tried formineral or chrome tanned leather. The commercial failure of the process was due to the fact that the oxalic acid had an insufficient solvent-action and formed insoluble salts with the lime which was used in the form of quicklim'e. Owing to their price it was out of the question to use other alkalies with such a process if it was to be carried out on an industrial scale. With the second process mentioned the sulfuric acid formed with the quicklime, which was also used, a plaster or gypsum mud, which rendered the worln'ng updifiicult and gave the glue produced a bad appearance. The tannin-ex- It required from thirty-six to forty days. The action of the sulfuric acid upon the spetches or glue materials was the chief reason why the quality and appearance of the glue obtained was not satisfactory. These drawbacks are entirely removed by the method or process according to the present invention. According to this process the leather or the leather-waste (it being here a question of mineral-tanned, and more especially of chrometanned leather-waste) is treated first with alkalies. With a view to chea ness, instead of alkalies there can also be use uicklime or the corresponding combinationo one of the other alkaline earths either alone or with a slight addition of alkali,for instance, soda.

After the treatment with-quicklime, which can be used as lime-milk or in any other composition desired, the leather cuttings are washed and laid in acid. For this muriatic acid is preferably employed; but any othermineral acids can also be used-such as fluorhydric acid, sulfurous acid, &c.either alone or combined with muriatic acid. An acid solution of a determined degree of concentra tion is used, according to the kind of acid. The acidfor instance, muriatic acidremoves the tannin not only from the leather- Waste, but also dissolves any mineral admixtures which may originate from the tanning,

.the action of quicklime and then of muriatic acid upon the waste saves a considerable furic ,acid only a common glue is obtained,

while the use of muriatic acid enables a good gelatin to be produced. If the process is to e unusually accelerated, the time therefor can be still further reduced by the use of meamount oftime, The detanning and boiling chanically-agitated vessels, such as are used in various manufacturing branches, and employed forthe detanning processes.

What I claim as my invention, and desire to secure by Letters Patent, is-

The method of preparing glue, which consists in subjecting chrome-tanned leather to the action of an alkaline solution, washing it thoroughly in water, steeping itwin murlatic acid, again carefully washing withflwater, 10 and finally neutralizing the resultant product. Y

\ In testimony whereof I have hereunto set my hand in resenoe of two witnesses. Y

ALB RT RUDOLF WEISS, JR.

Witnesses:

GUSTAV OEsNER, WILHELM R PPERs. 

